President Barack Obama’s ability to jam through appointments during the congressional break depends on one big factor: What the definition of “recess” is.

Since the holidays, GOP congressional leaders have used a handful of senators and a procedural technicality to keep their chamber active, gaveling in and out of session for a few minutes every two to three days. The strategy: Play keep-away with Obama’s power to fill confirmation-level jobs in their absence, the only way he can avoid almost-certain Republican filibusters of his nominees.

But some Obama allies and government watchdog groups want him to flex his constitutional muscle and declare the Senate is in recess if it’s inactive for less than three days or idle for perhaps even less than a minute. The bold counter-move would upend a long-held but legally murky congressional tradition, ratchet up tensions between Obama and the GOP and trigger fresh partisan fighting over the Senate’s advise-and-consent role — tit-for-tat warfare that probably would extend to already contentious judicial nominations.

Catholic University law professor Victor Williams, writing in The Huffington Post last week, decried Republicans’ de facto “nullification” of government and urged Obama to puncture the “myth” that an official congressional recess lasts three days or more. In a memo released Thursday, the liberal activist group People For the American Way declared the standoff “a chance [for Obama] to engage in a fight he can so obviously win.”

Ian Millhiser, a legal policy analyst at the left-leaning Center for American Progress, said the GOP’s continuous-session tactic “defies the rule of law” by blocking nominees. And liberal blogger Jonathan Bernstein declared in The Washington Post that no less than “presidential influence over the executive branch” is at stake.

“The American public has had enough,” Marge Baker, PFAW’s executive vice president for policy and programs, told POLITICO. “The level of obstruction he’s faced since he’s been in office — he’s been extraordinarily patient, far more than we would have wanted” since some vacancies, like those on the National Labor Relations Board, have impeded the function of government. “There’s a strong feeling on the part of a lot of people that it’s time to get the business of this country done,” she said.

The current recess showdown is likely to center on Richard Cordray, Obama’s choice to lead the Consumer Financial Protection Bureau, a watchdog agency that is the centerpiece of Obama’s financial overhaul legislation — and a new office that pro-business Republicans want to weaken by barring his appointment.

When Senate Minority Leader Mitch McConnell (R-Ky.) sidetracked Cordray’s nomination three weeks ago, Obama warned him and his Senate colleagues that he would “not take any options off the table” to put Cordray in place.

“We are not going to publicly speculate about recess appointments,” administration spokesman Eric Schultz told POLITICO in an email. Senate Republicans, he added, “have not been shy about their determination to block the president’s nominees and policy priorities. It is becoming more and more apparent that Republican obstructionism is an overtly political maneuver to thwart the president’s agenda.”

Republicans argue that Obama can’t unilaterally change the bipartisan understanding that a Senate recess lasts longer than three days — a position that Senate Democrats and even an Obama Justice Department official, former Acting Solicitor General Neal Katyal, seemed to accept.

A top GOP aide said Thursday that the Senate would continue to use procedural maneuvers to remain in session for the next three weeks.

“As he did for the entire last year of the Bush administration, [Senate Majority Leader Harry Reid] did not adjourn the Senate this month, so we are not in recess,” said a senior aide to Republican leadership, who spoke on background because the matter is politically volatile. “We will have pro forma sessions through Jan. 23, when the Senate resumes regular meetings. Since we are not in recess, there [can be] no recess appointments.”

The nominations — which also include selections for long-vacant federal judgeships, empty seats on the NLRB and Obama’s choice to lead the obscure federal Office of Procurement — are important, Schultz said, adding that the nominees “are exceptionally well-qualified, and we will push for their confirmations.”

Though Republicans are using the gavel-in, gavel-out tactic to stymie Obama, Senate Democrats deployed it quite effectively against George W. Bush when they held power during the last year of his presidency. In a report released last month, the nonpartisan Congressional Research Service reported that Bush “made no recess appointments between [Democrats’] initial pro forma sessions in November 2007 and the end of his presidency.”

Yet the Constitution doesn’t define the length of a recess, and “over time, the Department of Justice has offered differing views on this question, and no settled understanding appears to exist,” the CRS report said. In 1993, the report found, a Clinton-era Justice Department brief implied that the president “may make a recess appointment during a recess of more than three days.”

That establishes the precedent, Republicans say. They point to a statement Katyal made in 2010 during Supreme Court arguments in a case that touched on unfilled vacancies on the NLRB. Asked by Chief Justice John Roberts why the president could not bring the board to full strength during a Senate recess, Katyal replied, “I think our office has opined the recess has to be longer than three days.”

Just before Christmas, all 47 Senate Republicans signed a letter to Obama calling on him to refrain from recess appointments for the good of legislative branch-executive branch relations. Ignoring the warning, they wrote, “would, at the very least, set a dangerous precedent that would most certainly be exploited in future cases” involving Senate confirmation votes and “could needlessly provoke a constitutional conflict between the Senate and the White House.”

To underscore the point, McConnell sidetracked a series of noncontroversial nominees awaiting confirmation votes last month and offered Obama a deal: If you promise not to make recess appointments, I’ll allow those nominees to be approved.

“We are ready and willing to move forward, by consent, with a package of nominations to positions in both the executive and judicial branches,” McConnell said on the Senate floor. “Just as soon as I receive confirmation from the administration that it will respect practice and precedent on recess appointments, we can get these people confirmed.”

Obama rejected the deal.

Michael Gerhardt, a University of North Carolina law professor, said the president has much to gain, little to lose and is probably justified if he chooses to fight. The Constitution, Gerhardt said, isn’t specific about recesses; the existing vacancies are impeding important government functions; and the GOP’s threat to slow things down further is moot because “there’s [already] obstruction all over the place.”

Obama’s political adversaries “are already looking for ways to constrain his initiative and his nominations. Anything he does will be used against him,” said Gerhardt, who wrote a brief analyzing the situation for the left-leaning American Constitution Society. “I think in a way, this ought to liberate him to do the right thing as he sees it.”

Though Democrats hold the majority in the Senate, Congress doesn’t officially adjourn unless the Senate and the GOP-controlled House pass matching resolutions agreeing to do so, according to the CRS report. On May 25, weeks before the summer break, the report said, 20 Senate Republicans urged House Speaker John Boehner (R-Ohio) “to refuse to pass any resolution to allow the Senate to recess or adjourn for more than three days for the remainder of the president’s term,” pointing to Democrats’ use of the tactic against Bush.

While the White House won’t telegraph its counter-strategy, the push for Obama to exploit the crack in the GOP’s plan continues, particularly among liberal bloggers and left-leaning publications like Daily Kos and Talking Points Memo. Editorial boards of the Cleveland Plain Dealer in Ohio — Cordray’s home state and a key 2012 battleground — and The Washington Post, a sometimes White House antagonist, have called on the president to use his power for recess appointments.

Several analysts and observers, including HuffPo’s Jennifer Bendery, speculated that Obama could make his move as soon as Jan. 3 or use the time between the Senate’s mandatory end of the first half of the 112th session and the beginning of the second half on Jan. 23 — a theoretical window of as little as a minute — to appoint Cordray and perhaps several other stalled nominees.

Baker said there’s ample precedent for it: In 1948, she said, President Harry Truman pushed through recess appointments in the day or so between congressional sessions, and President Theodore Roosevelt filled more than 160 vacancies when Congress took a break that lasted “a little less than an hour.”

Obama, for his part, has repeatedly suggested he’ll go to the mat for Cordray and has dialed up public pressure on Republicans, signaling his willingness to fight.

During a surprise Dec. 8 White House press conference, Obama declared it makes “absolutely no sense” for the GOP to block the nomination and blamed Republicans for failing to protect consumers in a down economy. “Everybody says [Cordray] is highly qualified … a bipartisan individual who looks out for the public interest. This individual’s job is to make sure people are protected” from the financial abuses that triggered the economic meltdown.

“I want to send a message to the Senate: We are not giving up on this. We are going to keep going at it,” the president added. “We are not going to allow politics as usual on Capitol Hill to stand in the way of American consumers being protected from unscrupulous financial operators.”